The file doc/rear-release-notes.txt in upstream sources is CC-BY-ND-3.0,
which is not an allowed license for documentation. Therefore use a
modified tarball without this file. Add a Makefile to remove the file
and generate the modified tarball from the upstream tarball: invoke
make rear-%{version}-clean.tar.gz
while in the tarball's directory.
Adjust License: and %files accordingly.
Resolves: RHEL-26827
